Rocket powered launch vehicles (e.g., space launch vehicles) have been used for many years to carry human and non-human payloads into space. Rockets delivered humans into Earth orbit and to the moon, and have launched many satellites into Earth orbit or beyond. More recently, rockets have been used to launch unmanned space probes and to deliver supplies and personnel to the orbiting International Space Station.
Despite advances in manned and unmanned space flight, delivering astronauts, satellites, and other payloads to space continues to be very expensive. A reason is that all or portions of conventional launch vehicles are used only once. Such vehicles are referred to as “expendable launch vehicles” (ELVs). An example of an ELV is a conventional, multi-stage rocket that delivers a satellite to space: only the payload survives the journey and all other components are jettisoned or otherwise expended. An example of a partially reusable vehicle is the NASA space shuttle. The space shuttle's main external fuel tank is used only once whereas its main engines, two solid rocket boosters, and the space shuttle itself are reusable after substantial reconditioning. Although NASA's space shuttle is only partially expended and is largely reusable, reconditioning the reusable components is a costly and time consuming process that requires an extensive ground-based infrastructure.
As commercial interest in access to space increases, a need remains to reduce costs significantly. Various reusable launch vehicles (RLVs) have been proposed to reduce costs because a significant portion of such vehicles can be completely reused with much less reconditioning than the space shuttle requires.